A WLAN (Wireless Local Area Network) system works in an unauthorized frequency spectrum. Therefore, there may be another user who shares a frequency spectrum on a channel. If multiple users send data at the same time, mutual interference may occur, causing a conflict. Currently, the WLAN system uses a CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) mode to avoid a conflict. Carrier sense (CS) means that any device connected to a channel first performs sensing on the channel before the device is ready to send data. Data can be sent only when it is determined that the channel is idle. Multiple access (MA) means that multiple devices may visit a channel at the same time, and a data frame sent by one device may be received by multiple devices. In a CSMA/CA mechanism, a manner of active collision avoidance other than passive detection is used to resolve a conflict problem, which may meet a requirement for a case in which it is not easy to accurately detect whether a conflict occurs. An operation manner of CSMA is that when a device is ready to send a data frame and learns by sensing that a channel is idle, the data frame is sent only when the channel is still idle after another random period of time.
However, efficiency of an operation mode of the CSMA/CA is relatively low. In particular, in a case in which an AP (Access Point) and a STA (Station) are intensively deployed, a collision probability of channel contention greatly increases, and efficiency of MAC (Media Access Control) significantly decreases.